Techniques for forming burst cutting area mark

ABSTRACT

A BCA mark is applied prior to molding of optical recording media. A stamper including a BCA code is formed. The stamper including the BCA code is used in the molding of optical recording discs. This technique can be used in manufacturing of read-only type discs, recordable discs, rewritable discs, hybrid discs, discs readable from both disc sides, discs having multiple information layers, high-density discs, etc.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/687,101, filed Jun. 3, 2005 and entitled “METHOD AND APPARATUS FORAPPLYING BURST CUTTING AREA MARK PRIOR TO REPLICATION”.

TECHNICAL FIELD

This application relates to optical recording media. In particular, theapplication relates to application of a burst cutting area (BCA) markprior to molding of the optical recording media.

DESCRIPTION OF RELATED ART

Use of CDs (compact discs) and DVDs (digital versatile discs or digitalvideo discs) as optical storage media (“optical disc”) for storing andtransporting content (such as audio, video, graphics, computer software,etc.) in an optically readable manner has been popular for a number ofyears. Several formats of optical discs are currently available,including (A) read-only formats such as CD-DA (digital audio compactdisc), CD-ROM (CD-read-only memory), DVD-ROM, and other formats whereincontent is prerecorded on the disc (such as by using an injectionmolding process), and (B) recordable formats in the form of (i)write-once read-many times formats such as CD-R (CD-recordable), andDVD±R (DVD-recordable), etc., or (ii) rewritable formats such as CD-RW(CD-rewriteable), DVD-RAM (DVD-Random Access Media), DVD-RW or DVD+RW(DVD-rewriteable), PD (Phase change Dual disk) and other phase changeoptical discs. Optical disc players for these optical discs use a redlaser (with a wavelength range of 635 nm to 660 nm in the case of DVDand a wavelength of approximately 780 nm in the case of CD).

Optical discs using a blue laser (with a wavelength range of 400 nm to420 nm) have also been introduced, such as HD DVD and BD (each of whichincludes read-only, recordable and rewritable formats). The popularityof optical storage media driven by advancements in computer, informationcommunication and multimedia technologies has been accompanied also bydemands for a higher density and a greater capacity of optical storagemedia. HD DVD and BD provide high density formats which attempt to meetsuch demands.

In addition, optical media having plural information layers readablefrom the same side (for example DVD-9) or readable from both sides (forexample, DVD-10 and DVD-18), as well as hybrid optical media whichinclude a combination of formats, are also available.

In conventional read-only type optical discs (for example, CD-ROM,DVD-ROM, etc.), data is generally stored as a series of “pits” embossedin a plane of “lands”. Microscopic pits formed in a surface of a plasticmedium [for example, polycarbonate or polymethyl methacrylate (PMMA)]are arranged in tracks, conventionally spaced radially from the centerhub in a spiral track originating at the medium center hub and endingtoward the medium's outer rim. The light reflected from a read-onlymedium's surface in an optical disc player or reader varies according tothe presence or absence of pits along the information track. Aphotodetector and other electronics inside the optical disc playertranslate the signal from the transition points between these pits andlands caused by this variation into the 0s and 1s of the digital coderepresenting the stored information.

Read-only type optical discs generally are produced by an injectionmolding process. Initially, data representing the content to berecorded, encoded as a run length limited digital code (commonly knownas an EFM signal in CD manufacturing) which contains its digitalinformation in the timing between transitions, is used to control alaser beam recorder to form pits in a photoresist or a dye-polymer layeron an optical grade glass disc known as a glass master. A metallizedglass master is used in an electroforming process to form (typically,metal) stampers which are in turn used in injection molding of a pluralof optical recording discs.

In the molding process, a stamper is used on one side of an injectionmolding cavity to emboss an information layer of pits and lands on atransparent polymer substrate formed by injection molding. Theinformation bearing surface of the substrate is then covered with areflective film (of metal or alloy) or the like. In the case of a CD, aplastic protective coating is applied over the film, and then art (forexample, a picture, a design, text, etc.) is typically printed on theupper surface of the disc, to form an end product. In the case of DVDs,two half-thickness substrates are typically formed, metallization isapplied to one (for example, DVD-5) or both (for example, DVD-10, DVD-9,DVD-18) half-thickness substrates, and the two half-thickness substratesare bonded by an adhesive (for example, hotmelt adhesive, ultravioletlight-cured adhesive, etc.). A second information layer can be formedfor a DVD (for example, DVD-18) by applying a photo-polymer coating overa metallization layer applied to a substrate and the second informationlayer is embossed by a stamper into the photo-polymer layer which isthen UV cured, metallized and protective coated.

Recordable type optical media typically include a spiral wobble groovein the substrate. The groove defines recording channels on the disc forrecording data, provides information for tracking of the disc whilewriting or reading data, and has its wobble frequency modulated tocontain addressing and other information for the write and readprocesses. The substrate (including information layer bearing the spiralwobble groove) can be formed by injection molding, using a stamperelectroformed with a glass master. In addition, recordable-type opticalmedia generally include a recording layer, and in addition a reflectivelayer (of metal or alloy) and a protective layer, and may include otherlayers. Information is recorded in the recordable-type optical medium bydirecting a laser light beam modulated by signals to selectively changeoptical characteristics (reflectivity or extinction coefficient) of therecording layer. The recording layer in write-once read-many timesoptical media typically includes a photosensitive organic dye which isheated during recording to irreversibly form a pattern of marks or pitsinto the recording layer.

Each recording side of a rewritable disc also uses multiple layersbeginning with a polycarbonate plastic substrate containing a shallowspiral groove extending from the inside to the outside diameter of thedisc. A DVD-RW disc may additionally include pits and lands and aDVD-RAM disc also inside or alongside the groove itself. The substrates(including information layer bearing the spiral groove, land pre-pitsand embossed areas) may be formed by injection molding, using a stamperelectroformed with a glass master. Next in the multiple layers of arewritable disc typically comes a dielectric layer, followed by aphase-change type recording layer having a polycrystalline structure,another dielectric layer and a reflective layer (of metal or alloy).Additional layers may also be incorporated above or below the dielectriclayer, with a protective coating being applied as a last layer, and artmay be applied to at least one surface. During recording of therewritable optical medium, the laser selectively heats and allowscooling of tiny areas of the recording track to change the phase of eachheated area from more crystalline into less crystalline (also known as“amorphous”) phase, in order to create marks that can be called “pits”.During erase, the laser (in a process called “annealing”) changes theamorphous areas back into more crystalline areas.

HD-DVD format discs can be produced using a process similar to theprocess for forming a DVD disc, except that the minimum pit length isshorter and therefore the laser beam recorder used in the masteringprocess must be adapted to form the shorter pits.

BD format discs are typically manufactured by injection molding a 1.1 mmsubstrate with pits and sputtering a reflective layer over the pits toform an information layer, and applying a 0.10 mm transparent coverlayer over the information layer.

Various types of hybrid optical media are available. For example, onetype of hybrid media has data pit patterns prerecorded on a surface of asubstrate and has in addition a recording layer allowing a user torecord data to the recording layer. Further, optical recording mediahaving multiple recording layers are now also available. In addition, inanother hybrid optical recording disc a read-only area and a recordablearea are present on one side of the hybrid optical disc, with a wobblegroove in the read-only area modulated by depressions in the substrateand extending into the substrate in the recordable area. Each of thehybrid optical media has one or more reflective films (of metal oralloy) or the like.

The high capacity of optical recording media, coupled with recentenhancements to personal computers and the advent of recordable opticalmedia technology, renders optical media popular for illicit use. Forexample, unauthorized copying of proprietary and/or copyrighted,recorded content from optical media to optical media on a large scale(also referred to as “piracy”) is a growing concern. The piracytypically entails using software on a computer system having an opticalmedium drive to copy content from a recorded optical medium ontorecordable media such as CD-R or CD-RW (or DVD-R, DVD-RW or DVD+RW)discs.

Many copy protection techniques and devices have been proposed to limitcopying of content on optical media. Several of the proposed copyprotection techniques are discussed in commonly-owned U.S. applicationSer. No. 10/903,099, filed Jul. 30, 2004 and entitled METHOD ANDAPPARATUS FOR. PROTECTING AGAINST COPYING OF CONTENT RECORDED ON OPTICALRECORDING MEDIA, the entire contents of which are incorporated byreference herein.

Some optical recording media have a burst cutting area (BCA) which isspecified by the standards or specifications which govern those types ofoptical recording media. For example, the specifications for DIVX, DVDand HD-DVD, respectively, include provisions for a burst cutting area,intended for copy protection use. In the DIVX format, the burst cuttingarea is used on each disc for a disc identifier which uniquelyidentifies the disc.

The DVD specification which specifies the format of data on DVDsprovides for an optional Burst Cutting Area inside of the lead-in areaof a DVD, between an inner circumference of 22.3 mm+0/−0.4 mm and to anouter circumference of 23.5 mm+/−0.05 mm from the center of the centerhole of a disk. The Burst Cutting Area is intended to be a location on aDVD onto which a mark, such as a copy protection mark or code, or a barcode as a unique serial code for the DVD, can be written by a powerlaser (Annex K). It has been proposed that the serial code can be usedfor tracking DVDs and thereby also serve an objective of copyprevention. The DVD specification does not preclude the possibility ofrepeating the same mark on multiple discs of the same title.

A schematic representation of assorted areas of a DVD is illustratedexemplarily in FIG. 1A. The disk has a diameter of 120 millimeters witha center spindle hole of 15 millimeters. Adjacent to the spindle hole isa disk clamping area, depicted with dots, having minimum and maximumdiameters of 22 and 33 millimeters respectively. A guard band isprovided between the clamping area and a lead-in data area, depictedwith horizontal lines in FIG. 1A, (multiple dots in FIG. 1B) andoccupying an area between diameters of 45.2 and 48 millimeters. The dataor “program” area is shown with vertical stripes and is located betweendiameters of 48 and 116 millimeters, with a lead-out diameter of atleast 1 millimeter. To facilitate the individualization of disksfollowing mass production an area is provided where disk specific data,for example serial number or identification data can be added. Thisoptional marking area is known as the burst cutting area or BCA, and islocated between diameters of 44.6 to 47 millimeters (shown in FIG. 1Bbetween radii R1 and R3, respectively). All dimensions stated above arenominal, and omit allowable tolerances. Thus BCA data records arewritten within the lead-in data area of the disk.

Content Protection for Recordable Media (CPRM) is an option found insome DVD recorders that write DVD-RW and DVD-RAM discs using the DVDVideo Recording format (DVD-VR). Such an option allows materialspecifically flagged “copy once” to be written to a single disc butprevents that disc from then being further duplicated. This restrictionis accomplished by binding the content to the particular disc throughencryption employing, amongst other information, a code (mediaidentifier) unique to each writable disc compliant with the CPRM system.The code is inserted into the Burst Cutting Area (or Narrow BurstCutting Area or NBCA in the case of a DVD-RW) of the disc, to keep thedisc from being further duplicated by a DVD recorder.

U.S. Pat. Nos. 6,608,804, 6,641,886, 6,885,629, 6,891,788 and 6,894,962discuss assorted uses of a burst cutting area and types of informationwhich can be written in the burst cutting area. Some conventionaltechniques for writing and processing of data in a burst cutting areaare discussed in U.S. Pat. Nos. 6,052,465, 6,081,785, 6,414,920,6,453,420, 6,546,193, 6,708,299, 6,728,181, and in InternationalPublication No. WO98/58368. The entire contents of each of U.S. Pat.Nos. 6,052,465, 6,081,785, 6,414,920, 6,453,420, 6,546,193, 6,608,804,6,641,886, 6,708,299, 6,728,181, 6,885,629, 6,891,788 and 6,894,962, andInternational Publication No. WO98/58368 are incorporated herein inorder to more fully illustrate the state of the art as of the date ofthe subject matter described herein.

Conventionally, marks have been applied to a burst cutting area afterthe injection molding stage by cutting a mark with a low contrastrelative to the remainder of the disc, onto the reflective layer of thedisc. This approach requires either an offline process to apply the markto the burst cutting area or an inline BCA writer. Marks are typicallyplaced in the burst cutting area on DIVX discs, DVD discs and Gamecubediscs using these techniques. However, each process adds cost and timeto the process and the large expense of BCA marking equipment(approximately $500k per BCA writer).

SUMMARY

This disclosure discusses techniques for applying a BCA mark prior tomolding of the disc. In instances in which serialization of a BCA codeis not needed, the same BCA data can be placed on each of plural discsin a molding run, by applying the BCA mark on a metallized masteringsubstrate (made of, for example, glass, silicon, etc.), a father, amother or a stamper. The optical disc formed using the techniques ofthis disclosure comprises an information carrying area, a burst cuttingarea, and an embossed BCA mark formed at the burst cutting area.

The techniques of this application can be used in manufacturing ofread-only type discs, recordable discs, rewritable discs, hybrid discs,discs readable from both disc sides, discs having multiple informationlayers, high-density discs, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present application can be more readily understoodfrom the following detailed description with reference to theaccompanying drawings wherein:

FIG. 1A shows a schematic representation of an exemplary optical disc,such as a DVD;

FIG. 1B shows an exploded view of a cutout area in FIG. 1A;

FIG. 2 shows a flow chart of a creation process for a read-only typeoptical recording disc, according to an exemplary embodiment; and

FIG. 3 shows a flow chart of a method for applying a BCA mark prior tomolding of optical recording media, according to an exemplary embodimentof this disclosure.

DETAILED DESCRIPTION

The following discussion of exemplary embodiments of the techniques ofthis application is set forth to aid in an understanding of the subjectmatter of this disclosure, but is not intended, and should not beconstrued, to limit in any way the scope of this disclosure. Therefore,while specific terminology is employed for the sake of clarity indescribing some exemplary embodiments, the present disclosure is notintended to be limited to the specific terminology so selected, and itis to be understood that each specific element includes all technicalequivalents thereof.

The techniques of this disclosure include adding data to a burst cuttingarea (BCA) prior to molding which can be readable by the optical discdrive, such as for authentication purposes. This application providestools (in the form of methodologies, apparatuses, and systems) forapplying a burst cutting area (BCA) mark or code prior to molding of theoptical recording media, such as onto a mastering substrate, father,mother or stamper. The techniques of this disclosure avoids the use ofspecial-purpose BCA writer hardware (which cost approximately $500k)when serialization is not needed.

The terms “BCA mark” and “BCA code” are used herein interchangeably todenote any mark, code, cut or surface reflectance variation serving forcopy protection, disc identification or other information to be insertedin a burst cutting area (for example, BCA, NBCA, etc.) of a disc. It isknown in the art (and it has been proposed) that the burst cutting areacan be used for assorted purposes. The techniques of this applicationcan be used to apply BCA marks or codes for any of such purposes thatdoes not require serialization or varying other information in the BCAmark or code from disc to disc in a molding run.

An overview of optical recording disc creation, according to anexemplary embodiment, will be provided below with reference to FIG. 2.

Authoring (step S21) and pre-mastering (step S22) activities areperformed in order to preprocess content into a suitable form forgenerating an appropriate disc image for replication of read-only typeoptical discs. Preparation for applying a BCA mark may include applyingthe BCA mark to the disc image in pre-mastering.

It should be understood, however, that the techniques of thisapplication are not limited to creation of read-only type optical discsand can be applied to any optical recording disc which includes a burstcutting area, by applying a BCA mark or code prior to molding of theoptical recording media.

Mastering (step S23) is a process, following pre-mastering in the disccreation process, for creating a model, on a mastering substrate, of thefinal disc which is used for generating a stamper used in a mold formolding the optical media. Mastering includes reading a disc image(information) from a source media, and then formatting, encoding, andprocessing the information into a modulated data signal. The modulateddata signal is used to control a laser beam recorder to form pits andother marks, such as the BCA mark, in a photoresist or a dye-polymerlayer on an optical grade mastering substrate (of, for example, glass,silicon, etc.). As mentioned above, the BCA mark may be incorporated inthe disc image and therefore the modulated data signal would cause thelaser beam recorder to form the BCA mark in the mastering substrate.Alternatively, the BCA mark may be formed by the laser beam recorder inan additional pass over the mastering substrate, such as when the discimage does not include the BCA mark, or by another device for formingBCA marks.

In any event, the mastering substrate is covered with a metal layer (forexample, silver), and the metallized mastering substrate is used in anelectroforming process to form (typically, metal) stampers which are inturn used in the molding of a plural of optical recording discs.

In the electroforming process (step S24), a father is formed, forexample, by placing the metallized mastering substrate into a vesselcontaining a nickel sulphamate solution for a predetermined period oftime (for example, two hours) during which a layer of nickel is grownonto the metallized surface of the mastering substrate, and at the endof which a sheet of nickel, constituting the father, is separated fromthe surface of the metallized mastering substrate. The father is areverse image of the data and can be used to stamp discs. However, astamping device which becomes an integral part of a mold is subjected tomany stresses in the molding process. Accordingly, the father istypically not used to stamp discs since if it is damaged the entireprocess of creating a father would have to be repeated. Therefore, thefather is instead used to form a mother, by applying an electroformingprocess to the father to grow thereon a sheet of nickel constituting themother. The mother is separated from the father and in turn used in anelectroforming process to grow another sheet of nickel which constitutesthe stamper. The stamper, like the father, is a reverse image of thedata and therefore can be used in the injection molding of discs.Several stampers can be grown from a mother.

A method for applying a BCA mark prior to molding of optical recordingmedia, according to an exemplary embodiment (FIG. 3), includes forming astamper including a BCA code (step S31), and using the stamper includingthe BCA code in the molding of optical recording discs (step S33).

The BCA mark can be applied at the time of mastering by creating a solidgraphic mark that meets all of the physical specifications of BCAmarking parameters such as depth, width, length and spacing betweenmarks. The depth, width, length and spacing may be adapted toaccommodate contrast and shrinkage. The BCA mark can be mastered onto amastering substrate and thereby allows all of the molded discs tocontain the same BCA mark.

The laser beam recorder can be controlled appropriately to form such amark during mastering. As one example, the mark may be formed byapplying the laser beam recorder in a non-continuous spiral mode that istimed with a pulse per revolution signal according to the desired BCAmark.

Alternatively, the BCA mark can be applied during the electroformingprocess to a father, mother or stamper, by using, for example, a YAGlaser, and thereby avoid the need for BCA writer hardware for applying aBCA mark after the molding process.

After stampers are formed, a process (step S25) generally including thesteps of molding, metallizing, printing and testing is performed.

Methodologies and apparatuses which can be used in a manufacturingprocess are discussed in U.S. Pat. Nos. 4,995,799, 5,766,359, 5,766,495,5,792,538, 5,863,328, 5,900,098, 5,913,653, 5,932,042, 5,932,051,5,932,058, 5,935,673, 5,949,752, 5,958,651, 5,995,481, 5,997,976,6,117,284, 6,124,011, 6,160,787, 6,261,403, 6,309,496, 6,309,727,6,361,845, 6,440,248, 6,527,538 and 6,814,825, the entire contents ofeach of which are incorporated by reference herein.

The techniques of this disclosure can be applied to any of a broad rangeof optical discs, such as DVDs, high-density discs (for example, HD DVDand BD), etc., including any of the formats.

For example, the techniques of this disclosure may be applied to formstampers for use in molding optical discs that comply with therequirements of the BD read-only format. The stampers are used to forman information layer which includes a series of pits embossed in a planeof land, all of which being then covered by a reflective layer. Such aninformation layer typically comprises an information track having pitswith a minimum length along the track in a range of 138 nm to 160 nm,and comprises information marks configured for reading using a laserwith a wavelength in a range of 400 nm to 420 nm and a numericalaperture of 0.85. The burst cutting area of such a disc is in an annularregion of the disc at an inner radius of 21.0(+0.3/−0)mm and outerradius of 22.2(+0/−0.2)mm.

The techniques of this disclosure also may be applied to form stampersfor use in molding optical discs that comply with the requirements ofthe HD-DVD read-only format. The information layer of such discstypically comprises an information track comprising pits having aminimum length of approximately 204 nm and comprises information marksconfigured for reading using a laser with a wavelength in a range of 400nm to 420 nm and a numerical aperture of 0.65. The burst cutting area ofsuch a disc is in an annular region of the disc at an inner radius of22.3(+0/−0.4)mm and an outer radius of 23.15(+0.05/−0.05)mm.

Similarly, the techniques of this disclosure also may be applied to formstampers for use in molding optical discs that comply with therequirements of the DVD read-only format. The burst cutting area of sucha disc is in an annular region of the disc at an inner radius of22.3(+0/−0.4)mm and an outer radius of 23.50(+0.05/−0.05)mm.

In each instance, a BCA mark is formed in the stamper, and each discmolded using the stamper would also bear the BCA mark. The optical discformed using the techniques of this disclosure comprises an informationcarrying area, a burst cutting area, and an embossed BCA mark formed atthe burst cutting area.

The above specific embodiments are illustrative, and many variations canbe introduced on these embodiments without departing from the spirit orscope of the disclosure. For example, elements and/or features ofdifferent illustrative embodiments may be combined with each otherand/or substituted for each other within the scope of this disclosure.

1. A method for applying a BCA mark prior to molding of opticalrecording media, said method comprising: forming a stamper including aBCA code; and using the stamper including the BCA code in the molding ofoptical recording discs.
 2. The method of claim 1, wherein the BCA codeis applied to a mastering substrate, and the mastering substrateincluding the BCA code is used in a process for forming the stamper. 3.The method of claim 1, wherein the BCA code is applied to a father, andthe father including the BCA code is used in a process for forming thestamper.
 4. The method of claim 1, wherein the BCA code is applied to amother, and the mother including the BCA code is used in a process forforming the stamper.
 5. The method of claim 1, wherein the stamper isformed and then the BCA code is applied to the stamper.
 6. The method ofclaim 1, wherein the BCA code is included in a disc image formed inpremastering, the disc image including the BCA code is used to form amastering substrate, and the mastering substrate including the BCA codeis used in a process for forming the stamper.
 7. The method of claim 1,wherein the BCA code is applied to a mastering substrate after pits areformed in the mastering substrate, and the mastering substrate includingthe BCA code is used in a process for forming the stamper.
 8. Aread-only type optical disc comprising a BCA mark in a burst cuttingarea of the disc, wherein the BCA mark is formed using the method ofclaim
 1. 9. A recordable optical disc comprising a BCA mark in a burstcutting area of the disc, wherein the BCA mark is formed using themethod of claim
 1. 10. A rewritable optical disc comprising a BCA markin a burst cutting area of the disc, wherein the BCA mark is formedusing the method of claim
 1. 11. A hybrid optical disc comprising a BCAmark in a burst cutting area of the disc, wherein the BCA mark is formedusing the method of claim
 1. 12. An optical disc readable from bothsides and comprising a BCA mark in a burst cutting area of the disc,wherein the BCA mark is formed using the method of claim
 1. 13. Anoptical recording disc comprising a BCA mark in a burst cutting area ofthe disc, wherein said burst cutting area is in an annular region of thedisc at an inner radius of 21.0(+0.3/−0)mm and outer radius of22.2(+0/−0.2)mm, and wherein the BCA mark is formed using the method ofclaim
 1. 14. An optical recording disc comprising a BCA mark in a burstcutting area of the disc, wherein said burst cutting area is in anannular region of the disc at an inner radius of 22.3(+0/−0.4)mm and anouter radius of 23.15(+0.05/−0.05)mm, and wherein the BCA mark is formedusing the method of claim
 1. 15. An optical recording disc comprising aBCA mark in a burst cutting area of the disc, wherein said burst cuttingarea is in an annular region of the disc at an inner radius of22.3(+0/−0.4)mm and an outer radius of 23.50(+0.05/−0.05)mm, and whereinthe BCA mark is formed using the method of claim
 1. 16. An optical disccomprising: an information carrying area and a burst cutting area; andan embossed BCA mark formed at said burst cutting area.
 17. The opticaldisc of claim 16, wherein said embossed mark is formed while molding atleast a part of said disc.
 18. The optical disc of claim 16, whereinsaid burst cutting area is in an annular region of the disc at an innerradius of 21.0(+0.3/−0)mm and outer radius of 22.2 (+0/−0.2)mm.
 19. Theoptical disc of claim 16, wherein said burst cutting area is in anannular region of the disc at an inner radius of 22.3(+0/−0.4)mm and anouter radius of 23.15(+0.05/−0.05)mm.
 20. The optical disc of claim 16,wherein said burst cutting area is in an annular region of the disc atan inner radius of 22.3(+0/−0.4)mm and an outer radius of23.50(+0.05/−0.05)mm.